replace them both, if u reset n sends bad code replace otherone 4 real or go 2 a shop n spend 74 - 100 4 diagnostic
When I had that problem on my 1997 buick lesabre, I had to replace the catalyst converter and the 02 sensor on it. It resolved the issue with the code.
On a 2001 Buick LeSabre, there are typically two oxygen (O2) sensors. The upstream O2 sensor is located before the catalytic converter, attached to the exhaust manifold, while the downstream O2 sensor is positioned after the catalytic converter in the exhaust system. These sensors monitor the exhaust gases to help optimize fuel efficiency and emissions. To access them, you'll need to lift the vehicle and may require special tools due to their location.
02 sensor problem
If it is bad the check engine light will come on and set a code for that particular sensor.
Bank 1 sensor 1 was the upstream 02 sensor located before the catalytic con on my 03.
Replace fuel filter and check the 02 sensor if the check engine light is on it's probably the 02 sensor run a diagnostic test to be sure
Check your battery cables. Some computerized vehicles have to be reset. Disconnect the battery for about 5 minutes and then reconnect.
In the exhaust manifold or near the pipe, must raise car to get at it . better to work on when engine is cool,easer to to remove and you won't get burned.use never sieze if using old one again (new ones already have it on ) simply unscrews with wrench, do not force may damage threads
i doubt if you need an 02 sensor. try cleaning your mass air flow sensor with electronics celaner or brake cleaner first also check for vacuum leaks downstream from the maf
check the crank sensor
The check engine light would illuminate and the code set would help lead you to which sensor is at fault.
The check engine light will illuminate if you have a bad O2 sensor. The code set will lead you to the faulty sensor.